In this context, the known motorization components exhibit a changing or variable motorization torque demanding an over-motorization which results in shocks at the end of deployment.
These shocks can be significant and generate damage to the space appendages at the end of deployment, as well as stray torques damaging the piloting of the spacecraft. To mitigate this problem, the deployable structures can be dimensioned and reinforced so as to withstand the end-of-travel shocks generated in their deployment, but this solution is unsatisfactory and notably results in an increased weight for the complete structure.
Some lines of development have led to the devising of deployment mechanisms with almost zero resistive torque. Such mechanisms, such as the line of hinges described in the patent application FR 2635077, offer the advantage of requiring only little motorization power and generate minimized end-of-travel shocks. Other mechanisms are borne from enhancements made to the above mechanism, notably in terms of weight and volume. Such a deployment mechanism is disclosed in the patent application FR 0605653.
The known mechanisms, such as those described in the abovementioned patent applications FR 2635077 and FR 0605653, have an angular deployment capability that is limited to 180°. Moreover, their overall kinematics, because of their structure, generate very irregular motorization torques. Finally, the speed of deployment of the known deployment mechanisms, as already explained, results in a restoration of energy at the end of travel, and therefore a shock, because said speed of deployment is not regulated.
To correct these drawbacks, a motorization device has been proposed with controlled torque, described in the patent application published under the reference FR 2968234.Such a device makes it possible to offer an almost zero resisting torque, and is based on the use of flexible tracks that already exist in the system, to produce the motorization. A specific form is given to the flexible tracks so as to allow for an offsetting of the point of contact between the flexible tracks relative to the crossover point of winding means such as wound flexible blades or else cables, forming a link element between two substantially parallel, fitting-forming winding cylinders, to which various components of the system are linked. In this way, a torque dependent on the distance between the abovementioned point of contact and crossover point provokes mutual rotation of the flexible tracks, and the mutual rotation of the fittings. The “crossover point” between the link element-forming winding means should be understood in the wider sense to be the axis substantially parallel to the longitudinal axes or axes of revolution of the fittings, passing at the same time through the two winding means.
In the abovementioned device, a good control of the motorization torque presupposes a good control of the position of the point of contact between the flexible tracks, but it may in practice prove not so easy to thus control the position of the point of contact between the flexible tracks.